Rare-earth doped fluorides and process for preparing

Abstract

The invention is directed a composition represented by the chemical formula Eu x A 1−x F 2+x−2y O y wherein A is alkaline earth, 0.002≦x≦0.20, and 0≦y≦x; the composition exhibiting a luminescence spectrum characterized by peaks at 592±2 nm and 627±2 nm, wherein the ratio of the peak intensity at 592±2 nm to that at 627±2 nm is at least 5% larger than the corresponding peak intensity ratio at the same wavelengths of a first corresponding reference composition with the same value of x that has not been exposed to a temperature above 100° C., and wherein said ratio of the peak intensity at 592±2 nm to that at 627±2 nm is at least 5% smaller than the corresponding peak intensity ratio at the same wavelengths of a second corresponding reference composition with the same value of x that has been subject to heating to 900° C. for 6 hours.

1. A composition represented by the chemical formula
   Eu x A 1−x F 2+x−2y O y    
 
       wherein A is alkaline earth, 0.002≦x≦0.20, and 0≦y≦x; the composition exhibiting a luminescence spectrum characterized by peaks at 592±2 nm and 627±2 nm, wherein the ratio of the peak intensity at 592±2 nm to that at 627±2 nm is at least 5% larger than the corresponding peak intensity ratio at the same wavelengths of a first corresponding reference composition with the same value of x that has not been exposed to a temperature above 100° C., and wherein said ratio of the peak intensity at 592±2 nm to that at 627±2 nm is at least 5% smaller than the corresponding peak intensity ratio at the same wavelengths of a second corresponding reference composition with the same value of x that has been subject to heating to 900° C. for 6 hours. 
     
     
       2. The composition of  claim 1  wherein A is selected from Ca +2 , Ba +2 , or Sr +2 . 
     
     
       3. The composition of  claim 2  wherein A is Ca +2 . 
     
     
       4. The composition of  claim 2  wherein A is Sr +2 . 
     
     
       5. The composition of  claim 1  wherein 0.01≦x≦0.10. 
     
     
       6. A process comprising heating in the presence of oxygen a composition represented by the chemical formula
   Eu x   +3 A 1−x F 2+x−2y O y    
 
       wherein A is alkaline earth, 0.002≦x≦0.20, and 0≦y≦x; initially prepared at a temperature below 100° C., to a maximum temperature in the range of 200° C. to 900° C., followed by cooling to ambient temperature; with the proviso that the duration of heating not exceed six hours at 900° C., and with the further proviso that the composition so heated has not previously been exposed to the maximum temperature. 
     
     
       7. The process of  claim 6  wherein A is selected from Ca +2 , Ba +2 , or Sr +2 . 
     
     
       8. The process of  claim 7  wherein A is Ca +2 . 
     
     
       9. The process of  claim 7  wherein A is Sr +2 . 
     
     
       10. The process of  claim 6  wherein 0.01≦x≦0.10. 
     
     
       11. The process of  claim 6  wherein the heating is effected in a series of steps.